Hyperbaric oxygen therapy.

Hyperbaric oxygen therapy involves intermittent inhalation of 100% oxygen under a pressure greater than 1 atm. Despite over a century of use in medical settings, hyperbaric oxygen remains a controversial therapy. The last 20 years have seen a clarification of the mechanism of action of hyperbaric therapy and a greater understanding of its potential benefit. However, despite the substantial evidence that hyperbaric oxygen may have a therapeutic effect in certain carefully defined disease states, many practitioners remain unaware of these findings or are concerned about using hyperbaric therapy because of the controversy it has engendered. This review examines the indications currently considered appropriate for hyperbaric oxygen and briefly evaluates animal and clinical data substantiating these indications. Areas in which the mechanism of action of hyperbaric oxygen is still not well understood, as well as possible new areas of applications, are discussed.

Informed consent in emergency research. Prehospital thrombolytic therapy for acute myocardial infarction.

Can the conscious patient in the midst of a medical emergency provide adequate informed consent for a clinical research protocol? Adequate consent is crucial to the ethical conduct of clinical trials, including those performed in emergency settings. We examine the problem of emergency informed consent. As an illustrative case, we discuss a pilot trial of prehospital thrombolytic therapy for myocardial infarction. Federal regulations for clinical research do not provide clear guidelines on emergency research in the conscious patient. Clinical investigators currently approach emergency consent in four ways: (1) avoid such research, (2) omit the consent process, (3) obtain deferred consent, or (4) obtain customary consent. We suggest a fifth alternative, two-step consent, which permits the conduct of emergency research while protecting the rights of the emergency research subjects. Such a process may serve as an alternative solution for future studies faced with the problem of informed consent in emergencies.

KIE: The problem of informed consent to research in emergency care is examined, using as an example a pilot trial of prehospital administration of thrombolytic therapy for acute myocardial infarction. Current federal regulations governing emergency care research are reviewed, along with four ways in which investigators currently approach emergency consent. The authors' use of a two-step process to resolve the problem of emergency consent is described. This approach allows the conduct of emergency research while protecting the rights of research subjects, and may offer a solution to the the ethical conduct of other studies faced with the problem of consent to emergency care.

Evaluation of patients for the need of thrombolytic therapy in the prehospital setting.

Maximum benefit from thrombolytic therapy in acute myocardial infarction is obtained with early therapy. The earliest possible time to treat is during the initial evaluation of the patient in the home or ambulance, which requires accurate diagnosis of acute myocardial infarction in the prehospital setting. In our study, paramedics evaluated patients who had chest pain with a 12-lead ECG transmitted by cellular telephone and a checklist for inclusion and exclusion criteria for thrombolytic therapy. This information was transmitted to a hospital-based telemetry physician who diagnosed or excluded acute myocardial infarction and made a mock decision to withhold or administer a thrombolytic agent. Forty-eight patients with chest pain were evaluated. Six were diagnosed as having overt acute myocardial infarction by the hospital-based telemetry physician. All six patients had the diagnosis substantiated by both ECG and enzyme studies on hospital admission. Based on the data supplied by paramedics, two of these six patients were considered eligible for thrombolytic therapy by the physician. Hospital evaluation confirmed the prehospital decision to treat with a thrombolytic agent. In addition, all other patients were appropriately diagnosed as ineligible. Prehospital ECG diagnosis resulted in two patients going directly to the catheterization lab, thereby bypassing the emergency department. Overt acute myocardial infarction can be accurately identified by a prehospital-acquired 12-lead ECG transmitted to a hospital-based physician. Our study demonstrates that in conjunction with specially trained paramedics, the hospital physician can decide whether to administer thrombolytic therapy to such patients in the prehospital setting.

Effect of spontaneous sighs on arterial oxygenation during isoflurane anesthesia in humans.

The presence, frequency, and volume of spontaneous sighs was evaluated in 21 (ASA 1-2) supine patients aged 44 +/- 15.2 (SD) yr, during isoflurane-nitrous oxide anesthesia. Before induction the inspiratory capacity of each patient was determined. After induction of anesthesia and tracheal intubation patients breathed spontaneously except for three manual inflations to each patient's predetermined inspiratory capacity at the beginning and end of surgery. Arterial blood gas tensions were measured before and 5 min after each set of mechanical deep breaths and each hour during surgery, the mean duration of which was 2 +/- 0.09 hr. Spontaneous sighs occurred in 13 of 21 patients. The average frequency was 6 +/- 4 sighs/hr. At FIO2 = 0.5, nonsighing patients had an initial PaO2 of 229 +/- 59 mm Hg and sighers had an initial PaO2 of 162 +/- 57 mm Hg (P less than 0.05). Arterial oxygen did not change in sighing patients during the course of surgery, while in nonsighing patients the PaO2 decreased from the initial value of 229 +/- 60 mm Hg to 170 +/- 63 mm Hg (P less than 0.05). Mechanical deep breaths administered at the end of surgery produced no improvement in oxygenation in either sighers or nonsighers. The presence or absence of sighs did not correlate with PaO2 or PACO2. Though the results suggest that spontaneous sighs in some patients may function to help maintain arterial oxygenation, all patients maintained their PaO2 while breathing spontaneously under general anesthesia in the supine position.

Change in auditory asymmetry with amobarbital: evidence of cerebral pharmacological asymmetry?

Eleven right-handed subjects were administered a dichotic listening test to assess cerebral hemispheric dominance, both under a drug-free condition and following systemic injection of the barbiturate, amobarbital. The finding of increased right ear advantage during the drug period reflects increased left cerebral dominance, and suggests that amobarbital may have an asymmetric, pharmacological effect on the two cerebral hemispheres.